Crankcase lubricant and chemical compound therefor



Patented Mar. 14, 1944 UNETED CRANKCASE LUBRICANT AND CHEMICAL COUND THEREFOR No Drawing. Application November 8, 1941, Serial No. 418,326

6 Claims.

This invention relates to a new class of chemical compounds which are useful as addition agents to lubricating oils of the type known as crankcase oil; i. e. hydrocarbon oils of relatively low viscosity and pour point such as are used in the crankcases of internal combustion engines and to lubricating oils of this type containing such additives. More particularly, the invention relates to the heavy metal salts of the dicapryl ester of dithiophosphoric acid and to lubricating oils of the above type containing this class of compounds. By the term heavy metal salt in the following specification and claims we mean the salts of the metallic elements of groups II to VlJI inclusive of the periodic system and especially such salts as those of the alkaline earth metals magnesium, calcium, strontium and barium and other metals such as zinc, aluminum, chromium, tin, cobalt and nickel which form water-insoluble salts with dicapryl dithiophosphate. Salts of lithium, sodium, potassium, rubidium and caesium, the alkali metals, are excluded from th invention.

The heavy metal salts of dicapryl dithiophosphoric acid ester are water-insoluble but hydrocarbon oil-soluble compounds. Most of the compounds of this class, including all the alkaline earth metal salts are brownish-yellow solids of low melting point, whereas the zinc salt is a viscous liquid at ordinary temperatures. The compounds as a class are soluble in hydrocarbon oils of the type of Ill-W grade lubricating oils to the extent of -50% by weight, and are therefore well adapted for manufacture and sale in the form of lubricating oil. solutions or fairly high concentration, which can be readily blended with further amounts or oil to concentrations of 9.1-3 in which they are used.

We have discovered that lubricating oil containing 0.14% of heavy metal salts of the dicapryl ester of dithiophosphoric acid possess several remarkable and unexpected properties. We have found that these compounds are detergents for the prevention of sludge deposits in truck. bus, aeroplane and marine gasoline and Diesel englues, and that they also possess extremely importantnon-oxidizing or antioxidant properties when compared with other metal salt detergents that have previously been used. Moreover, these compounds possess a remarkable degree of stability against decomposition and sludge formation under the conditions of heavy duty use in lubricating oil when it is considered that they are esters of aliphatic secondary alcohols of a type that are known to be considerably less heatstable than the esters of the corresponding primary alcohols.

Dicapryl dithiophosphoric acid is prepared by reacting capryl alcohol with phosphorous pentasulfide in the ratio of approximately 4 moles of the alcohol for each mole of Past, the reaction being carried out by heating the two ingredients.-

together at 95 C. with stirring for about 2 /2 hours. When the evolution of H28 has subsided the resulting dicapryl dithiophosphoric acid ester is dissolved in a mixture of absolute alcohol and benzene and suflicient heavy metal oxide is added to eil'ect neutralization. The mixture is heated to complete the neutralizatlonand a part of the solvent is evaporated to expel the water of neu- -tra1ization, whereupon the solution is filtered and the filtrate evaporated to recover the product. When an alkaline earth metal oxide is used in this manner the alkaline earth metal salts so obtained have the following probable structural formula The corresponding salts of metals of higher va lency, such as the aluminum and chromium salts have similar structural formulas in which three or more thiophosphoric acid ester radicals are linked through sulfur to the metal.

As is noted above one of the most important features of our invention resides in the addition to lubricating oils of the type of hydrocarbon crankcase oils of the heavy metal salts of the above-defined class, either alone or in admixture with other ingredients, in amounts sumcient to exert sludgedispersina p perties under heavy duty service conditions. Th formation of sludge in crankcase oils is intimately related to the pro-- be used to'combat oxidation and decomposition n the lubricating oil, and oils containing the ieavy metal dicapryl dithiophosphates in are with either or both or these comp ntitute another important feature of our invenion.

The invention will be further illustrated in letail by the following specific examples, which meant results obtained with a representative ieavy metal salt of dicapryl dithiophosphate. It should be understood, however, that the inrention in its broader aspects is not limited to base examplesl Example 1 260 parts by weight of capryl alcohol iCH: (CH2) sCH(OH) CH3] were stirred rapidly with 111 parts by weight of Finely ground Pass and heated at 80-95" C. for about 2% hours. At the end of this time practically all of the P285 was reacted and the dicapryl dithiophosphoric acid remained as a brown liquid. 354 parts by weight of the prodnot so obtained were dissolvedin a. mixture of equal parts of absolute ethyl alcohol and benzene and stirred rapidly while 77 parts by weight of powdered barium oxide were added to effect neutralization. The mixture was warmed to complete the neutralization and then heated to boiling and a part of the solvent was evaporated to expel the water of neutralization. The solution was then filtered from any traces of barium salts and the filtrate evaporated. The barium dicapryl dithiophosphate was recovered as a brownish-yellow crystalline material of low melting point, insoluble in water but soluble to the extent of about 50% in l0-W grade Pennsyl- Vania, (parafiin base) lubricating oil.

The corresponding zinc salt was prepared by adding 41 parts by weight of finely powdered zinc oxide to a solution of 354 parts of dicapryl dithiophosphoric acid in an alcohol-benzene mixture as ,described above. The product was obtained as a. thin oily liquid which was easily soluble in lubricating oil.

Example 2 samples of the oilunder test are pouredinto these tubes and air at the rate of liters per hour is ones-sea dure are shown in the following table, wherein oil A was a solvent refined l0-W grade oil and oil B was a phenol-extracted iii-W grade oil.

A. P. I. gravity Naphtha 2 2 5 Neat. oxlg ilzed insoluble CwPb ho.

Per cent Oil A 201 Oil A-HL6% Ba dlcapryl dithiophosphate is Oil B Z3. 5 17.17 215 1. El Oil B+0A% Ba dicapryl dlthlophosphate +22 Oil B+0.6% Ba diczipryl dithiophosphate. 27. 3 3. 02 +16 3. i9

This application is a continuation-in-part of our copending application, Serial No. 4015960, filed July 11, 194A.

What we claim is:

1. A solution of a heavy metal salt of the dicapryl ester of dithiophosphoric acid in lubricating oil.

2. A solution of an alkaline earth metal salt of the dicapryl ester of dithiophosphoric acid in lubricating oil.

3. A solution of the barium salt of the dicapryl ester of dithiophosphoric acid in lubricating oil.

4. A lubricating oil composition comprising a crankcase oil having dissolved therein ill-3% of a heavy metal salt of the dicapryl ester of dithiophosphoric acid.

5. A lubricating oil composition comprising a crankcase oil having dissolved therein (ll-3% of an alkaline earth metal salt of the dicapryl ester of dithiophosphoric acid.

6. A lubricating oil composition comprising a crankcase oil having dissolved therein (Ll-3% of the barium salt of the dicapryl ester of dithiophosphoric acid.

ELIWER W. COOK. WILLIAM D. THOMAS, JR. 

